The present invention relates to a Lysholm compressor.
FIGS. 1 and 2 schematically show a conventional Lysholm compressor. Intermeshing male and female rotors 1 and 2 are rotatably accommodated in a casing 3 with a plurality of helical thread crests 1a on the male rotor 1 being in mesh with a plurality of helical thread roots 2a on the female rotor 2. The rotors 1 and 2 are rotated in opposite directions indicated by arrows in FIGS. 1 and 2 so that a gas 4 is sucked at an axial end of the compressor, is compressed between the rotors 1 and 2 and is discharged through the other axial end of the compressor. The rotors 1 and 2 are supported at their respective shafts 5, 6 and 7, 8 extending from opposite axial ends of the rotors 1 and 2, by the casing 3 through bearings 9, 10 and 11, 12, respectively.
Gas compression efficiency in such Lysholm compressor is extremely greatly affected by inter-lobe clearance C1 between the rotors 1 and 2; by tip clearance C2 between the casing 3 and outermost peripheries of the rotors 1 and 2; by discharge-side end clearance C3 between the casing 3 and discharge-side end faces 1x and 2x of the rotors 1 and 2; and by suction-side end clearance C4 between the casing 3 and suction-side end faces 1y and 2y of the rotors 1 and 2. It is therefore very important to properly set or select these clearances C1, C2, C3 and C4.
The clearances C1, C2, C3 and C4 are not of simple nature and cannot be uniformly set or selected from mechanical size relationship. In the Lysholm compressors, consideration must be taken to a demand for decreasing the discharge-side end clearance C3 as small as possible because of the gas 4 from suction-side end faces of the rotors being gradually compressed to have highest pressure at the discharge end; to thermal expansions of the rotors 1 and 2 caused by the heat resulting from the compression of the sucked gas 4; and to plays of the bearings 9, 10, 11 and 12 in radial and thrust directions. Bearing in mind all of these, clearance distribution must be set or selected to optimize the compression efficiency.
The present invention was made to overcome the above and has for its object to provide a Lysholm compressor in which the above-mentioned clearances can be properly set or selected.